Machines such as, for example, off-highway haul trucks, motor graders, snow plows, and other types of heavy equipment are used to perform a variety of tasks. Some of these tasks involve carrying or pushing large, awkward, loose, and/or heavy loads up steep inclines or along rough or poorly marked haul roads. And, because of the size and momentum of the machines and/or because of poor visibility, these tasks can be difficult for a human operator to complete effectively.
To help guide the machines along the haul roads and keep the machines within appropriate lanes on the haul roads, some worksites utilize earthen berms located at the sides of the haul roads. The berms act as borders of the haul road, providing a visual indication of the edge of the road and functioning to either redirect the machine back onto the road or hinder further movement off of the road, should the machine deviate from an appropriate lane. Although effective, the use of the earthen berms alone may be insufficient to keep some large or heavily loaded machines on the haul roads and, in some situations, may damage the machines when the machines contact the berms. As such, an alternative or additional method for keeping the machines within the appropriate lanes of a haul road may be necessary.
One such method is described in U.S. Pat. No. 6,038,496 (the '496 patent) issued to Dobler et al. on Mar. 14, 2000. Specifically, the '496 patent describes a vehicle provided with laterally mounted optical scanning devices for zero-contact scanning of a lateral highway area, and an evaluation unit connected thereto. The optical scanning devices each comprises a linear array of infrared transmitting devices located side-by-side, and a corresponding charge-coupled device (CCD) array. The connected evaluation unit is programmed to perform time measurement, contrast measurement, and contour recognition based on input from the CCD array. With this optical scanning system, an operator may be warned of lane deviation or automatic lane maintenance can be provided, with different reactions to various lane boundaries being possible.
During operation of the optical scanning system described in the '496 patent, the system scans the lateral surface of the highway (i.e., an area to the sides of the vehicle) to detect any existing lane boundary, a type of lane boundary (i.e., a painted stripe, a curb, or a corrugated strip), and a nature of an area outside of the lane boundary (i.e., another travel lane, a breakdown lane, or a highway boundary). A running time and contrast determination permit recognition of lateral lane markings, and determination of the distance of the vehicle therefrom. The optical scanning system then functions to either warn an operator when the distance from the vehicle to the lateral lane marking deviates from a value preset by the driver, or automatically maintains the preset distance value in a manner similar to conventional cruise control regulating. Based on the type of lane boundary, the warning provided by the optical scanning system can change. For example, when the lane boundary is a corrugated strip, the warning is an audible sound similar to that of a rumble strip, suggesting to the driver that the lane marking is studded with bumps or provided with corrugated strips. Similarly, the warning is adjusted based on the area outside of the lane boundary, for example if that area can be driven on. Based on the area outside of the lane boundary, a timing of the warning is adjusted to allow the driver sufficient time and space to keep the vehicle on the highway or to return it thereto.
Although the optical scanning system of the '496 patent may improve guidance of a vehicle, it may be expensive and limited. Specifically, the infrared transmitting devices and CCD array are costly. In addition, the optical scanning system may be unable to detect an area on an opposing side of a raised earthen berm to determine if that area can be driven on. As such, the optical scanning system cannot properly adjust the warning provided to the operator or autonomously control the vehicle based on the detection. Further, the optical scanning system of the '496 patent does not take into account conditions that could affect maneuverability of the vehicle. In addition, the optical scanning system of the '496 patent only affects steering of the vehicle, which may be insufficient to control the vehicle in some situations.
The disclosed guidance system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.